Analysis of Trace Metals in Human Hair by Laser-Induced Breakdown Spectroscopy with a Compact Microchip Laser.

Yuji Matsuura,Makoto Nakagawa

doi:10.3390/s21113752

Abstract

A laser-induced breakdown spectroscopy (LIBS) system using a microchip laser for plasma generation is proposed for in-situ analysis of trace minerals in human hair. The LIBS system is more compact and less expensive than conventional LIBS systems, which use flashlamp-excited Q-switched Nd:YAG lasers. Focusing optics were optimized using a Galilean beam expander to compensate for the low emitted pulse energy of the microchip laser. Additionally, hundreds of generated LIBS spectra were accumulated to improve the signal-to-noise ratio of the measurement system, and argon gas was injected at the irradiation point to enhance plasma intensity. LIBS spectra of human hair in the UV to near IR regions were investigated. Relative mass concentrations of Ca, Mg, and Zn were analyzed in hairs obtained from five subjects using the intensity of C as a reference. The results coincide well with those measured via inductively coupled argon plasma mass spectrometry. The lowest detectable concentrations of the measured LIBS spectra were 9.0 ppm for Mg, 27 ppm for Zn, and 710 ppm for Ca. From these results, we find that the proposed LIBS system based on a microchip laser is feasible for the analysis of trace minerals in human hair.

Highlights

Laser-induced breakdown spectroscopy (LIBS) is a technique that measures emission spectra from luminous plasma generated by irradiation with nano, pico, and femto-second laser pulses and is useful for multi-elemental analysis of various target materials [1,2]
A microchip laser [3,4,5,6] that emits a pulse energy of hundreds of microjoules has become popular because it makes the LIBS system more compact and lower in cost than conventional systems, which use flashlamp-excited Q-switched Nd:YAG lasers [7,8]
One of the advantages of the LIBS technique is that pretreatment of samples is not required, unlike in other elemental analysis methods such as inductively coupled argon plasma-atomic emission spectroscopy (ICP-AES) or mass spectrometry (ICP-MS) [15]

Summary

Introduction

Laser-induced breakdown spectroscopy (LIBS) is a technique that measures emission spectra from luminous plasma generated by irradiation with nano-, pico-, and femto-second laser pulses and is useful for multi-elemental analysis of various target materials [1,2]. One of the advantages of the LIBS technique is that pretreatment of samples is not required, unlike in other elemental analysis methods such as inductively coupled argon plasma-atomic emission spectroscopy (ICP-AES) or mass spectrometry (ICP-MS) [15] For healthcare applications, such as nutritional status monitoring, analysis of harvested biological specimens, such as nails and hair, is useful. This is because conventional Q-switched Nd: YAG lasers can obtain relatively high plasma intensity by irradiation with pulse energy of more than 10 mJ, which is necessary to detect trace elements in hair The use of these lasers makes the LIBS system large in scale and not easy to handle. The concentration results coincide well with those measured via ICP-MS

Materials and Methods

CaCaI I

Ca II Ca I

Ca II

Accumulation number

ZZnn II

Ca Mg Zn

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